Bosch Sensortec Community

    cancel
    Showing results for 
    Search instead for 
    Did you mean: 

    BM280 stability

    BM280 stability

    Johanan
    New Poster

    Hello,

    I am trying to measure the pressure inside a box (about 1x1x1 meters), which has a few fans taking air out.

    The measured range is 10 to 50 pa. I use 2 BMP280 devices, one outside the box, one inside the box.

    I calibrate the difference when no fan is on, I get 0 pa.

    Whoever after some time, there is a drift, which I cant explain. I read the data sheet many times, and it seems that I should be able to get an accurate measurement, but I have seen drifts of 30 pa difference with no fan working on a stable system.

    I am using "Ultra high resolution" prs oversampling x16, Temp. Over sampling x2, IIR coefficient x16, and I even add my own IIR of x32 is my software. Sample delay is 0.5ms , as power consumption is not an issue.

    Stile, I have this drift.

    What am I missing? Is there some particular PCB layout needed (I followed all recommendations on data sheet, my PCB has only 3 mounting holes and so on.

    Thanks

    Johanan

    6 REPLIES 6

    hor63
    Member

    IMHO you have chosen a bad design from the start.

    the pressure difference is at the lower end of the resolution of the absolute pressure sensors.

    You should use a differential pressure sensor with an appropriate rage ( e.g. 100PA). Here your pressure difference is the full range of the sensor, and not a minuscule part like in your design.

    Well, you are correct that I am starching it, but I am still within the data sheet specifications.

    according to my settings, in ultra high resolution, and IIR cof. I set, the nois in pressur measurment shuld be 0.2 pa.

    I  avarge this more by my own IIR, and still get fluctuations  3 pa, and slow drifts of 6 - 8 pa in a short time.

    So I wonder if the data sheet is inaccurate, or I am doing something wrong, or I misunderstand the data sheet.

    Price of differential sensors for this range is much higher then BMP280 or BMP388.

     

    I think you indeed misinterpreted the datasheet. This is short term drift, which is greatly improved in BMP388.

    Noise is not the only important parameter.

    o_o

    It is true that this was a test project, which I wanted to see if it can be done.

    Unfortunately the BMP388 pin out is different, but I will be happy to edit the pcb. Do you think the 388 can do a much better job in such application?

    Thanks.

    Icon--AD-black-48x48Icon--address-consumer-data-black-48x48Icon--appointment-black-48x48Icon--back-left-black-48x48Icon--calendar-black-48x48Icon--center-alignedIcon--Checkbox-checkIcon--clock-black-48x48Icon--close-black-48x48Icon--compare-black-48x48Icon--confirmation-black-48x48Icon--dealer-details-black-48x48Icon--delete-black-48x48Icon--delivery-black-48x48Icon--down-black-48x48Icon--download-black-48x48Ic-OverlayAlertIcon--externallink-black-48x48Icon-Filledforward-right_adjustedIcon--grid-view-black-48x48IC_gd_Check-Circle170821_Icons_Community170823_Bosch_Icons170823_Bosch_Icons170821_Icons_CommunityIC-logout170821_Icons_Community170825_Bosch_Icons170821_Icons_CommunityIC-shopping-cart2170821_Icons_CommunityIC-upIC_UserIcon--imageIcon--info-i-black-48x48Icon--left-alignedIcon--Less-minimize-black-48x48Icon-FilledIcon--List-Check-grennIcon--List-Check-blackIcon--List-Cross-blackIcon--list-view-mobile-black-48x48Icon--list-view-black-48x48Icon--More-Maximize-black-48x48Icon--my-product-black-48x48Icon--newsletter-black-48x48Icon--payment-black-48x48Icon--print-black-48x48Icon--promotion-black-48x48Icon--registration-black-48x48Icon--Reset-black-48x48Icon--right-alignedshare-circle1Icon--share-black-48x48Icon--shopping-bag-black-48x48Icon-shopping-cartIcon--start-play-black-48x48Icon--store-locator-black-48x48Ic-OverlayAlertIcon--summary-black-48x48tumblrIcon-FilledvineIc-OverlayAlertwhishlist